The present invention relates to the field of plant molecular biology, more particularly to regulation of gene expression in plants.
Expression of heterologous DNA sequences in a plant host is dependent upon the presence of an operably linked promoter that is functional within the plant host. Choice of the promoter sequence will determine when and where within the organism the heterologous DNA sequence is expressed. Where continuous expression is desired in cells throughout a plant, promoters driving plant-wide constitutive expression are utilized. In contrast, where gene expression in response to a stimulus is desired, inducible promoters are the regulatory element of choice. Where expression in specific tissues or organs are desired, tissue-preferred promoters may be used. That is, they may drive expression in specific tissues or organs. Expression mediated by such tissue-preferred promoters may be constitutive or inducible. In either case, additional regulatory sequences upstream and/or downstream from the core promoter sequence may be included in expression constructs of transformation vectors to bring about varying levels of expression of heterologous nucleotide sequences in a transgenic plant.
Frequently it is desirable to have constitutive or inducible expression of a DNA sequence in particular tissues or organs of a plant. For example, increased resistance to pathogens of a plant might be accomplished by genetic manipulation of the plant""s genome to comprise a tissue-preferred promoter operably linked to a heterologous gene such that proteins which enhance resistance to pathogens are produced in a desired tissue of the plant.
Alternatively, it might be desirable to inhibit expression of a native DNA sequence within a plant""s tissues to achieve a desired phenotype. In this case, such inhibition might be accomplished with transformation of the plant to comprise a tissue-preferred promoter operably linked to an antisense nucleotide sequence, such that expression of the antisense sequence produces an RNA transcript that interferes with translation of the mRNA of the native DNA sequence.
The SF3 gene encodes a pollen-specific protein. It has four zinc finger domains organized into two LIM domains. A LIM domain is a double zinc finger in which the last ligand of the first zinc finger is separated from the first ligand of the second zinc finger by two amino acids. The LIM motif could be directly involved in nucleic acid binding. The SF3 protein may be involved in controlling pollen-specific transcription, translation and/or mRNA transport (Baltz et al. (1992) Plant cell 4: 1465-1466; Baltz et al. (1996) Sex. Plant Reprod. 9: 264-268). A cDNA encoding the SF3 protein has been described in Baltz et al. (1 992) Plant J. 2: 713-721.
Manipulation of expression of genes in reproductive tissues of plants can be used to manipulate plant fertility, control pollination and improve hybrid seed production. For example, see U.S. Pat. Nos. 5,795,753; 5,086,169; 5,545,546; 5,728,926.
Thus, isolation and characterization of pollen-preferred promoters that can serve as regulatory regions for expression of heterologous nucleotide sequences of interest in a pollen-preferred manner are useful for genetic manipulation of plants, particularly, for the manipulation of male fertility in plants.
Compositions and methods for regulating expression of heterologous nucleotide sequences in a plant are provided. The compositions are novel nucleotide sequences for pollen-preferred plant promoters, more particularly the region regulating transcriptional initiation isolated from the plant gene SF3. A method for expressing a heterologous nucleotide sequence in a plant using the transcriptional initiation regulation sequence disclosed herein is provided. The method comprises transforming a plant cell with a transformation vector that comprises a heterologous nucleotide sequence operably linked to the plant promoters of the present invention and regenerating a stably transformed plant from the transformed plant cell. In this manner, the promoter sequences are useful for controlling the expression of endogenous as well as exogenous products in a pollen-preferred manner.
Downstream from and under the transcriptional initiation regulation of the pollen-specific region will be a sequence of interest which will provide for modification of the phenotype of the pollen. Such modification includes modulating the production of an endogenous product, as to amount, relative distribution, or the like or production of an exogenous expression product to provide for a novel function or product in the pollen.